Field of the Invention
The present invention relates to a communication system, an image forming apparatus, and a method of controlling the image forming apparatus, and more particularly to a communication system that controls supply of electric power, an image forming apparatus, and a method of controlling the image forming apparatus.
Description of the Related Art
There has been known a communication system in which a client PC and a digital front end (hereinafter referred to as the “DFE”) as an image processing apparatus are connected to each other via a network, and the DFE and an MFP (Multifunction Peripheral) as an image forming apparatus are connected to each other via a network. In the communication system, instructions for performing various kinds of processing, such as a print instruction for executing print processing, are transmitted from the client PC. For example, when the print instruction is transmitted from the client PC, the DFE generates print data for executing the print processing based on the print instruction, and transmits the generated print data to the MFP. The MFP executes the print processing based on the transmitted print data. During a time period over which such processing is not performed, in order to reduce power consumption of the whole communication system, the DFE and the MFP shift to a power-saving mode in which power consumption can be reduced than in a normal mode for performing the various kinds of processing. Upon shifting to the power-saving mode, the DFE and the MFP each supply electric power only to minimum necessary components provided therein. Each of the DFE and the MFP having shifted to the power-saving mode returns from the power-saving mode to the normal mode e.g. in response to a user operation of a console section thereof.
Here, it is desired that the DFE and the MFP speedily return from the power-saving mode to the normal mode, and to realize the speedy return from the power-saving mode to the normal mode, there has been known, for example, a technique in which as soon as the MFP returns from the power-saving mode to the normal mode, the DFE is caused to return from the power-saving mode to the normal mode in an interlocked manner (see e.g. Japanese Patent Laid-Open Publication No. 2009-043243).
However, in the technique disclosed in Japanese Patent Laid-Open Publication No. 2009-043243, there occur cases where the DFE is unnecessarily caused to return from the power-saving mode to the normal mode. For example, when a user operates the MFP to perform copy processing or FAX processing, thereby causing the MFP to return from the power-saving mode to the normal mode, it is possible to perform the copy processing or the FAX processing using only the MFP without performing data communication with the DFE, but in this case as well, the DFE is caused to return from the power-saving mode to the normal mode in a manner interlocked with the return of the MFP. This results in hindrance to the reduction of power consumption.